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    08|案例篇--系统中出现大量不可中断进程和僵尸进程怎么办？（下） | 迪克猪的博客
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    <h2 class="title">08|案例篇--系统中出现大量不可中断进程和僵尸进程怎么办？（下）</h2>
    <div class="post_content">
      <h3 id="问题">问题</h3>
<p>通过分析 top 命令的输出，我们发现了两个问题：</p>
<ul>
<li>第一，iowait 太高了，导致系统平均负载升高，并且已经达到了系统 CPU 的个数。</li>
<li>第二，僵尸进程在不断增多，看起来是应用程序没有正确清理子进程的资源。</li>
</ul>
<h3 id="iowait分析">iowait分析</h3>
<ul>
<li>dstat可以同时查看 CPU 和 I/O 这两种资源的使用情况</li>
</ul>
<p><img src="../../images/20200531-1743-40.png" alt=""></p>
<ul>
<li>strace 正是最常用的跟踪进程系统调用的工具。</li>
</ul>
<div class="highlight"><pre style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4"><code class="language-bash" data-lang="bash">$ perf record -g
$ perf report
</code></pre></div><h3 id="僵尸进程">僵尸进程</h3>
<p>找出父进程，然后在父进程里解决。</p>
<div class="highlight"><pre style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4"><code class="language-bash" data-lang="bash"><span style="color:#75715e"># -a 表示输出命令行选项</span>
<span style="color:#75715e"># p表PID</span>
<span style="color:#75715e"># s表示指定进程的父进程</span>
$ pstree -aps <span style="color:#ae81ff">125</span>
</code></pre></div><p><img src="../../images/20200531-1748-13.png" alt=""></p>
<h3 id="小结">小结</h3>
<p>iowait 高不一定代表 I/O 有性能瓶颈。当系统中只有 I/O 类型的进程在运行时，iowait 也会很高，但实际上，磁盘的读写远没有达到性能瓶颈的程度。</p>
<p>碰到 iowait 升高时，需要先用 dstat、pidstat 等工具，确认是不是磁盘 I/O 的问题，然后再找是哪些进程导致了 I/O。</p>

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    <div class="info post_meta">
      <time datetime=2020-05-31T17:31:56&#43;0800 class="date">Sunday, May 31, 2020</time>
      
        <ul class="tags">
        
          <li> <a href="https://zsy619.github.io/tags/linux%E6%80%A7%E8%83%BD%E4%BC%98%E5%8C%96">linux性能优化</a> </li>
        
          <li> <a href="https://zsy619.github.io/tags/linux">linux</a> </li>
        
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